Abstract The light-dependent modulation of cytoskeletal proteins, such as tubulin and actin, with photoswitchable ligands is a powerful approach to controlling cellular functions and could lead to a new class of cancer chemotherapeutics. The parent project describes approaches for developing photoswitchable inhibitors, with which to manipulate actin dynamics. A challenge with this approach is that these interactions involve proteins that have a high tendency to polymerize and are difficult to measure with conventional methods, especially when irradiation is involved. A new approach is, therefore, required for rational design of photoswitchable inhibitors and nucleators. In this Administrative Supplement, we request funding to purchase a Microscale Thermophoresis instrument to characterize photoswitchable ligand binding interactions before and after irradiation. The system would significantly enhance our ability to address the specific goals in the parent grant and enhance impact of several projects at NYU. Funds for the purchase of this equipment were not requested in the original submission because MST?s improved capabilities for protein-ligand complex characterization were not anticipated.